Cd^(2+)、乙草胺单一及其复合污染对少根紫萍生理生化特性的影响

Single and the synthetic effects of Cd^(2+) and the acetochlor on the physiological behaviors of Spirodela oligorrhiza

为进一步了解重金属和农药复合污染对水生植物产生毒害作用的机制,以少根紫萍叶片叶绿素质量比、过氧化物酶活性(POD)、超氧化物歧化酶活性(SOD)、丙二醛(MDA)含量为指标,通过水培试验研究了少根紫萍在镉、乙草胺污染胁迫4 d后的生理生化响应,并探讨了镉、乙草胺单一与复合污染对少根紫萍叶片的毒性效应及其致毒机制。结果表明,单一镉污染时,随镉质量浓度的增加,叶绿素质量比显著降低。叶绿素质量比对镉污染响应敏感,有潜力作为水体镉毒性效应的监测指标。随着镉质量浓度的增加,少根紫萍叶片SOD、POD酶活性表现为先增加后降低的趋势;MDA含量随镉质量浓度的增加而显著增加。乙草胺单一处理对少根紫萍各项指标的影响与镉相似,但均小于镉对少根紫萍的影响。镉-乙草胺复合污染时,叶绿素质量比变化趋势与单一处理相同,并低于相应的单一镉、乙草胺处理;但同一镉质量浓度下不同乙草胺质量浓度处理组间叶绿素质量比差异不显著,Cd2+对叶绿素的破坏占主导。镉-乙草胺复合污染处理时,SOD、POD活性仍表现为先增加后下降趋势,但与镉单一处理时比较有降低现象;MDA含量仍随质量浓度的增加而增加,且高于单一处理。镉-乙草胺复合污染的毒性效应高于单一污染的毒性效应,表现为协同作用。

The paper would like to bring about the research results on the single and the synthetic effects of Cd2＋ and the acetochlor on the physiological behaviors of Spirodela oligorrhiza in hoping to expound the toxicity mechanism of the mixed heavy metals and pesticides on the aquatic plants.For this purpose,we have also conducted experiments with the content of chlorophyll,the activity of SOD,POD and that of MDA in the leaves of Spirodela oligorrhiza for tracing the biological responses of Spirodela oligorrhiza leaves to the single and joint stress of cadmium（Cd） and acetochlor.The results of the above mentioned experiments verify that the single-Cd treatment has significant effects on the content of chlorophyll.For example,with the increase of Cd concentrations,the content of chlorophyll tends to decrease evidently with the stress content of chlorophyll being a sensitive index in the response to it.With the increase of Cd,the SOD and POD activities of Spirodela oligorrhiza leaves tend to reveal an increase-and-decrease tend,with the POD activities turning to be higher than the CK whereas the content of MDA keeps rising constantly.However,similar effect of the single treatment of Spirodela oligorrhiz acetochlor can be found on Cd,though it should be less than to it,because under the integrated stress of Cd-acetochlor,the content of chlorophyll tends to decrease with the increase of its concentration,and less than in the single-Cd stress,though no striking concentration difference of chlorophyll between the groups of different acetochlor concentrations at the same Cd concentration.This shows that Cd2＋ is the dominant factor in the destruction of chlorophyll.There can be found an increasing-decreasing trend of the Spirodela oligorrhiza leaf SOD and POD activities,at the expense of the decrease of such enzyme activities as compared with the single-Cd stress,for the POD activities turned to be lesser than CK.In addition,with the increase of the content of MDA,its concentration would also increase,and turn to be higher than the single-Cd stress,which suggests that the combined toxicity of Cd and acetochlor should be stronger than the single-Cd stress.Therefore,the interaction of cadmium and acetochlor turns to be a synergic action,and the accumulation of O-2 and ·OH proves to be one of the main causes that accounts for the Cd-acetochlor combined toxicity.